LABORATORY WORK No 4

Performed by:

Radek Chatrny, Jakub Prasek

Conditions:

t = 20.5 °C;  p = 1018.5 hPa;  φ = 48 %

Topic:

Density  of  Liquid  Foods

Tasks:

1.

Determine the density of liquid substances used in cooking.

2.

Compare the density of various liquid foods by means of bar chart.

Theory:

Density of a liquid is a quantity defined by proportion of mass m [kg] and volume V [m³] of  the liquid. The derived unit of density is  kg/m³.

The density of liquids can be measured for example with hydrometer. The hydrometer is a hollow weighed glass tube that changes on the top into a narrow sealed tube with scale on which the consistence of  liquid is determined. Hydrometer mustn´t touch either the bottom or the sides while submerged into the measured liquid. The less the density of the liquid, the deeper the hydrometer is dipped. It dips less in a dense liquid. The heavier the hydrometer, the more it dips in the liquid.

The consistence of liquids depends on temperature. The density of warmer liquids is mostly smaller.

Aids:

Hydrometers, graduated vessel, 250 cm³ of liquid foods according to the chart.

Procedure:

1.

Pour about 250 cm³ of investigated liquid  food into a narrow graduated vessel.

2.

Dip the hydrometer into the liquid.

3.

Determine the consistence of liquid food in kg/m³ on the scale of the hydrometer.

4.

Make up a bar chart in which the length of the column is directly proportional to the density r [kg/m³].

5.

Determine the liquid with the biggest and the smallest density from the chart. Compare the density of  foods with the consistence of water.

Picture:

water with density
1000 kg/m³

liquid with density
bigger than water

 liquid with density
smaller than water

Chart:

Number of measuring

Food

Density ρ [kg/m³]

1.

drinking water

1000

2.

vinegar

1200

3.

orange juice

1150

4.

         concentrated fruit syrup

1380

5.

           low-fat long life milk

834

6.

Pepsi cola

1200

7.

vegetable cooking oil

920

Graph:

Conclusion:

From the measured foods in the household,  the fruit syrup had the biggest density [1380 kg/m³], the low-fat long life milk had the smallest density [834 kg/m³]. Vinegar, juice and cola had bigger density than water, cooking oil and milk had smaller density.